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Fully Delocalized Mixed-Valent Cu1.5Cu1.5 Complex: Strong Cu-Cu interaction and Fast Electron Self-Exchange Rate Despite Large Structural Changes** |
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| Authors: | Dr. Yang Liu Dr. Stefan G. Resch Haowei Chen Dr. Sebastian Dechert Dr. Serhiy Demeshko Dr. Eckhard Bill Prof. Dr. Shengfa Ye Prof. Dr. Franc Meyer |
| Affiliation: | 1. Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany;2. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 P. R. China Department of Chemistry, Tsinghua University, Beijing, 100084 P. R. China Contribution: Data curation (equal), Formal analysis (equal), Validation (equal), Writing - original draft (equal);3. Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany Contribution: Formal analysis (supporting), Investigation (supporting), Writing - review & editing (supporting);4. Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34–36, 45470 Mülheim an der Ruhr, Germany;5. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 P. R. China |
| Abstract: | A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, CuICuI ( 1 ) and mixed-valent Cu1.5Cu1.5 ( 2 ). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD-DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1 ) and a very high delocalization energy of 13 000 cm−1, comparable to the mixed-valent state of the biological CuA site. Electron self-exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1 , viz. 1′ ; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self-exchange closely related to the function of the CuA site. |
| Keywords: | Conformational Change CuA Site Electron Self-Exchange Macrocyclic Ligands Mixed-Valent Cu1.5Cu1.5 |